The present invention relates to the production of petroleum, and more particularly to a method and apparatus for producing extremely viscous crude oil from underground reservoirs.
Little by little, the world's easily found and easily produced petroleum energy reserves are becoming exhausted. Consequently, to continue to meet the world's growing energy needs, ways must be found to locate and produce much less accessible and less desirable petroleum sources. Wells are now routinely drilled to depths which, only a few decades ago, were unimagined. Ways are being found to utilize and economically produce reserves previously thought to be unproducible (e.g., extremely high temperature, high pressure, corrosive, sour, and so forth). Secondary and tertiary recovery methods are being developed to recover residual oil from older wells once thought to be depleted after primary recovery methods had been exhausted.
Some crude oils (or, more broadly, reservoir fluids) have a low viscosity and are relatively easy to pump from the underground reservoir. Others have a relatively low viscosity at elevated reservoir temperatures, but become viscous as they cool while being produced. Still others have very high viscosities even at reservoir conditions. It is not uncommon, therefore, for example in California, to find wells with considerable quantities of valuable crude which have nevertheless been shut in because it was too expensive to produce the viscous crude by pumping it out.
A need therefore remains for a new and improved method and apparatus which will change the economics of producing such highly viscous crudes so that these valuable energy reserves can be economically and efficiently produced. Preferably, such a method and apparatus will be uncomplicated and straightforward in design and implementation, versatile, durable, and readily suited to utilization in the widest possible range of viscous crude pumping environments.